1. Technical Field
The present invention relates to electrooptic devices and electronic apparatuses.
2. Related Art
With regard to liquid crystal devices, it is known that, when light enters a liquid crystal material, an oriented film or the like included therein, various kinds of ionic impurities are generated through photochemical reactions and cause degradation in display quality of the liquid crystal device such as uneven display and the like. In a liquid crystal device used as a light valve of a projector, liquid crystal, oriented films, and so on included therein need higher light resistance because the luminous flux density of incident light is much higher than that in the case of a direct-view-type liquid crystal device. In order to realize a high light resistance, it is necessary to suppress ionic impurities which are generated as a result of light irradiation and cause a defect in display and the like from being integrated in a display area.
It is also known that the following ionic impurities diffuse into a display area depending on driving operation, difference in temperature and the like of liquid crystal and cohere therein so as to cause degradation in display properties; that is, an ionic impurity mingled with liquid crystal when the liquid crystal is injected into a liquid crystal device, an ionic impurity eluted from a sealing material or an end-sealing material surrounding a liquid crystal layer, and so on. In particular, in the case where an inorganic oriented film made of silicon oxide or the like is used, impurities are likely to be adsorbed to the outer edge of the display area, whereby a blur, unevenness, or the like can be generated due to localized impurities.
Meanwhile, liquid crystal devices that include measures for trapping ionic impurities in liquid crystal layers are publicly known (JP-A-5-323336, JP-A-2000-221521, JP-A-8-201830, JP-A-10-123526, JP-A-2008-58497, JPA-2008-89938). The liquid crystal devices described in JP-A-5-323336, JP-A-2000-221521, JP-A-8-201830 and JP-A-10-123526 are devices in which a pair of electrodes is formed on interior surfaces of a pair of substrates holding a liquid crystal layer, and ionic impurities in the liquid crystal layer are trapped by an electric field generated in the depth direction of the liquid crystal layer (longitudinal electric field) between the pair of electrodes. The liquid crystal devices described in JP-A-2008-58497 and JPA-2008-89938 are devices in which a pair of electrodes is formed side by side on one of a pair of substrates holding a liquid crystal layer, and ionic impurities in the liquid crystal layer are trapped by an electric field generated in the substrate surface direction (transverse electric field) between the pair of electrodes.
However, in the liquid crystal devices described in JP-A-5-323336, JP-A-2000-221521, JP-A-8-201830 and JP-A-10-123526, because the pair of electrodes is disposed opposing each other while holding a liquid crystal layer that is as much as a few micrometers thick, it has been difficult to generate a strong electric field between the electrodes so as to enhance efficiency of the trapping. On the other hand, in the liquid crystal devices described in JP-A-2008-58497 and JP-A-2008-89938, a relatively strong electric field can be generated with ease; however, because an equipotential plane is formed along a direction in which comb-tooth shape electrodes extend, there has been a problem in that it is difficult to trap ionic impurities moving along the direction in which the above electrodes extend.